ZK91587: a novel synthetic antimineralocorticoid displays high affinity for corticosterone (type I) receptors in the rat hippocampus

In vitro cytosol binding assays have shown the properties of binding of a novel steroid, ZK91587 (15 beta, 16 beta-methylene-mexrenone) in the brain of rats. Scatchard and Woolf analyses of the binding data reveal the binding of [3H] ZK91587 to the total hippocampal corticosteroid receptor sites with high affinity (Kd 1.9 nM), and low capacity (Bmax 17.3 fmol/mg protein). When 100-fold excess RU28362 was included simultaneously with [3H] ZK91587, the labelled steroid binds with the same affinity (Kd 1.8 nM) and capacity (Bmax 15.5 fmol/mg protein). Relative binding affinities (RBA) of various steroids for the Type I or Type II corticosteroid receptor in these animals are: Type I: ZK91587 = corticosterone (B) greater than cortisol (F); Type II: B greater than F much greater than ZK91587. In the binding kinetic study, ZK91587 has a high association rate of binding in the rat (20.0 x 10(7) M-1 min-1). The steroid dissociates following a one slope pattern (t 1/2 30 h), indicating, the present data demonstrate that in the rat hippocampus, ZK91587 binds specifically to the Type I (corticosterone-preferring/mineralocorticoid-like) receptor.     

Intracellular CBG-like molecules in the rat pituitary

The localization of transcortin (CBG) in pituitary cells of the rat was investigated using the peroxydase-antiperoxydase (PAP) technique. A rabbit antiserum against purified rat plasma transcortin was used as the primary antiserum. Transcortin-like (CBG-like) immunoreactive products were found in the cytoplasma of certain cells in the anterior pituitary, but not in the intermediate lobe and weakly in the posterior pituitary. It is postulated that the CBG-like molecules participate in the cellular uptake process of corticosterone, thereby modulating the feedback signal of this steroid on pituitary function.     

Steroids and electrical activity in the brain

Corticosteroid hormones can enter the brain and bind to two receptor subtypes: the high affinity mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR) with approximately 10-fold lower affinity. Under physiological conditions the degree of receptor occupation will range from a predominant MR occupation (at the beginning of the inactive period, under rest) to concurrent activation of MRs and GRs (at the circadian peak and after stress). With in vitro electrophysiological recording techniques we observed that neuronal excitability in the CA1 hippocampal field is under a long-term control of MR- and GR-mediated events. The predominant occupation of MRs is associated with a stable amino acid-carried synaptic transmission; calcium- and potassium-currents are small, as are the responses to biogenic amines. Occupation of GRs in addition to MRs results in a gradual failure of CA1 neurons to respond to repeated stimulation of amino acid-mediated input; ionic conductances and responses to biogenic amines are large. In general, electrical properties recorded when both MRs and GRs are unoccupied (i.e. after adrenalectomy) resemble the responses observed when both receptor types are activated. The corticosterone dependency of electrical properties is thus U-shaped. We conclude that MR occupation may be responsible for the maintenance of information processing in the CA1 field and the stability of the circuit. Additional activation of GRs will initially suppress synaptic activity, but may eventually result in an increased instability and even vulnerability of the neuronal networks.     

Binding of corticosteroid receptors to rat hippocampus nuclear matrix.

In rat hippocampus, the mineralocorticoid receptor and the glucocorticoid receptor bind corticosterone with high affinity. We have studied the association of these receptors with the nuclear matrix both after in vivo and in vitro administration of radiolabelled corticosterone to hippocampus cells. It was found that in vivo 100% and in vitro 60% of the corticosterone that specifically bound to rat hippocampus nuclei was attached to the nuclear matrix. A selective glucocorticoid receptor agonist did not compete for corticosterone binding. This indicates that this binding was mediated by the mineralocorticoid receptor rather than the glucocorticoid receptor.     

Biotransformation of endorphins by a synaptosomal plasma membrane preparation of rat brain and by human serum.

β-Endorphin (β-LPH 61–91), γ-endorphin (61–77), des-tyrosine-γ-endorphin (62–77), α-endorphin (61–76), and β-LPH 61–69 either labeled with [¹²⁵I] at the N-terminal 61-tyrosine residue or unlabeled were incubated with a crude synaptosomal plasma membrane fraction of rat brain or in human serum. At different time intervals the release of [¹²⁵I]-tyrosine or the change in immunoreactivity of the endorphins was determined. The cSPM preparation displayed both high aminopeptidase and endopeptidase activities. In contrast, human serum mainly contained aminopeptidase activity. The data suggest that functional endorphin metabolism may occur at the synaptosomal plasma membrane. These membranes may potentially be involved in the formation of behaviorally active endorphin fragments.     

A putative glucocorticoid receptor and a transcortin-like macromolecule in pituitary cytosol.

This study describes the binding of [3H]corticosterone and [3H] dexamethasone to soluble macromolecules in the pituitaries of adrenalectomized rats perfused at sacrifice to remove blood contamination. (1) Unlabeled dexamethasone competes only slightly for [3H] corticosterone binding when the steroids are added to cytosol as well as when the steroids are present from the time of disruption of the tissue. In the latter case, corticosterone is as good a competitor as dexamethasone for [3H]dexamethasone binding. (2) Gel permeation chrmatography with BioRad A-5M reveals the presence of a [3H] corticosterone-macromolecular complex with an elution volume comparable to transcortin as well as a very large hormone-binding complex eluting in the void volume of the column...     

Lipidomics of familial longevity

Middle‐aged offspring of nonagenarians, as compared to their spouses (controls), show a favorable lipid metabolism marked by larger LDL particle size in men and lower total triglyceride levels in women. To investigate which specific lipids associate with familial longevity, we explore the plasma lipidome by measuring 128 lipid species using liquid chromatography coupled to mass spectrometry in 1526 offspring of nonagenarians (59 years ± 6.6) and 675 (59 years ± 7.4) controls from the Leiden Longevity Study. In men, no significant differences were observed between offspring and controls. In women, however, 19 lipid species associated with familial longevity. Female offspring showed higher levels of ether phosphocholine (PC) and sphingomyelin (SM) species (3.5–8.7%) and lower levels of phosphoethanolamine PE (38:6) and long‐chain triglycerides (TG) (9.4–12.4%). The association with familial longevity of two ether PC and four SM species was independent of total triglyceride levels. In addition, the longevity‐associated lipid profile was characterized by a higher ratio of monounsaturated (MUFA) over polyunsaturated (PUFA) lipid species, suggesting that female offspring have a plasma lipidome less prone to oxidative stress. Ether PC and SM species were identified as novel longevity markers in females, independent of total triglycerides levels. Several longevity‐associated lipids correlated with a lower risk of hypertension and diabetes in the Leiden Longevity Study cohort. This sex‐specific lipid signature marks familial longevity and may suggest a plasma lipidome with a better antioxidant capacity, lower lipid peroxidation and inflammatory precursors, and an efficient beta‐oxidation function.     

Loss of the gene for the alpha subunit of ATP synthase (ATP5A1) from the W chromosome in the African grey parrot (Psittacus erithacus)

This study describes the results of an analysis using Southern blotting, the polymerase chain reaction, and sequencing which shows that the African grey parrot (Psittacus erithacus) lacks the W-chromosomal gene for the alpha subunit of mitochondrial ATP synthase (ATP5A1W). Additional evidence shows that in other psittacines a fragment of the ATP5A1W gene contains five times as many nonsynonymous nucleotide replacements as the homologous fragment of the Z gene. Therefore, whereas in these other psittacines the corresponding ATP5A1Z protein fragment is highly conserved and varies by only a few, moderately conservative amino acid substitutions, the homologous ATP5A1W fragments contain a considerable number of, sometimes highly nonconservative, amino acid replacements. In one of these species, the ringneck parakeet (Psittacula krameri), the ATP5A1W gene is present in an inactive form because of the presence of a nonsense codon. Other changes, possibly leading to an inactive ATP5A1W gene product, involve the substitution of arginine residues by cysteine in the ATP5A1W protein of the mitred conure (Aratinga mitrata) and the blue and gold macaw (Ara ararauna). The data suggest also that although the divergence of the psittacine ATP5A1W and ATP5A1Z genes preceeded the origin of the psittacidae, this divergence occurred independently of a similar process in the myna (Gracula religiosa), the outgroup used in this study. Received: 6 September 2000 / Accepted: 7 March 2001     

Neurophysiological Effects of Sleep Deprivation in Healthy Adults,a Pilot Study

Total sleep deprivation (TSD) may induce fatigue, neurocognitive slowing and mood changes, which are partly compensated by stress regulating brain systems, resulting in altered dopamine and cortisol levels in order to stay awake if needed. These systems, however, have never been studied in concert. At baseline, after a regular night of sleep, and the next morning after TSD, 12 healthy subjects performed a semantic affective classification functional magnetic resonance imaging (fMRI) task, followed by a [¹¹C]raclopride positron emission tomography (PET) scan. Saliva cortisol levels were acquired at 7 time points during both days. Affective symptoms were measured using Beck Depression Inventory (BDI), Spielberger State Trait Anxiety Index (STAI) and visual analogue scales. After TSD, perceived energy levels, concentration, and speed of thought decreased significantly, whereas mood did not. During fMRI, response speed decreased for neutral words and positive targets, and accuracy decreased trendwise for neutral words and for positive targets with a negative distracter. Following TSD, processing of positive words was associated with increased left dorsolateral prefrontal activation. Processing of emotional words in general was associated with increased insular activity, whereas contrasting positive vs. negative words showed subthreshold increased activation in the (para)hippocampal area. Cortisol secretion was significantly lower after TSD. Decreased voxel-by-voxel [¹¹C]raclopride binding potential (BP_ND) was observed in left caudate. TSD induces widespread cognitive, neurophysiologic and endocrine changes in healthy adults, characterized by reduced cognitive functioning, despite increased regional brain activity. The blunted HPA-axis response together with altered [¹¹C]raclopride binding in the basal ganglia indicate that sustained wakefulness requires involvement of additional adaptive biological systems.     

Post-training reward partially restores chronic stress induced effects in mice

Reduced responsiveness to positive stimuli is a core symptom of depression, known as anhedonia. In the present study, we assessed the expression of anhedonia in our chronic stress mouse model using a subset of read-out parameters. In line with this, we investigated in how far chronic stress would affect the facilitating effect of post-training self-administration of sugar, as we previously observed in na?ve mice. Male C57BL/6J mice were repeatedly and at unpredictable times exposed to rats (no physical contact) over the course of two weeks. Following novelty exploration, (non-) spatial learning and memory processes with and without post-training sugar acting as reinforcer, emotionality, reward sensitivity and corticosterone levels were determined. We found that (1) the effects of chronic stress persisted beyond the period of the actual rat exposure. (2) Post-training self-administration of sugar as reinforcer improved spatial performance in na?ve mice, whereas (3) in stressed mice sugar partially "normalized" the impaired performance to the level of controls without sugar. Chronic stress (4) increased behavioral inhibition in response to novelty; (5) induced dynamic changes in the pattern of circadian corticosterone secretion during the first week after rat stress and (6) increased the intake of sucrose and water. (7) Chronic stress and sugar consumed during spatial training facilitated the memory for the location of the sucrose bottle weeks later. Concluding, our chronic stress paradigm induces the expression of anhedonia in mice, at different levels of behavior. The behavioral inhibition appears to be long lasting in stressed mice. Interestingly, sugar consumed in close context with spatial learning partially rescued the stress-induced emotional and cognitive impairments. This suggests that reward can ameliorate part of the negative consequences of chronic stress on memory.